Topic 5 & 5 Vestibular system and Vestibular anatomy

Question 1

Pathways from vestibular nuclei

Answer 1

MLF (medial longitudinal fasiculus)-
extraoccular eye movement VOR head thrust

Vestibulospinal tract- posture

Vestibulocollic tracts- head position
( from spinal accessory nerve)

Vestibulothalamocortical- Conscious awareness of position

Vestibulocerebellar- coordination

Vestibuloautonomic- nausea and vomiting

Question 2

Role of optokinetic reflex and VOR

Answer 2

VOR- keeps gaze fixed on an object even if head is moving

Optokinetic- Compensation for the motion of the visual feild to preserve stable vision

Uses relative velocity of image on retina to induce eye movements in the same direction at the same velocity

Question 3

Nystagmus
Define
Explain diff bn central and peripheral

Answer 3

named after fast component

Fast phase to the left caused by:
rotation of head to the left
Movement of eyes to right to track an object
Cool water in R ear
pathology over stimulating the left and under stimulating the right

Central ( e.g MLF) MS

• vertical or rotational(pendular)
• direction changing fast phase changes with direction of gaze
• doesn’t reduce with fixation

Peripheral( eg vestibular neuritis)
-Horozontal & jerk?
Beats faster with gaze in direction of fast phase
Beats slower with gaze ....
Reduces with fixation
Associated with BPPV

Question 4

Components of the vestibular system

Answer 4

Vestibular apparatus

• static labyrinths( utricle & saccule in vestibule)
• Kinetic labyrinths(semicircular ducts in semicircular canals

Vestibular nerve

4 vestibular nuclei (on floor of rhomboid fossa)

6 vestibular pathways

Question 5

The vestibular apparatus
what is the difference between static and kinetic labyrinths and boney and membranous

Also structure

Answer 5

STRUCTURAL

• Bony labyrinth ( vestibule & semicircular canals
• Membranous labyrinth (utricle, saccule, semicircular ducts, cochlear duct)

FUNCTIONAL
-kinetic labyrinth
(semicircular ducts in semicircular canals)

-Static labyrinth
(Utricle + saccule in vestibule )

Question 6

Role of static labyrinths

Answer 6

To respond to linear acceleration and decelleration

Contains:
Macula utriculi-HOROZONTAL mvmt

Macula S acculi- S AGGITAL mvmt

made up of sensory epithelium with sensory hair cells known as kinocillium

Question 7

Role of kinetic labyrinths

also structure

Answer 7

Responds to angular acceleration and decelleration

where semicircular ducts comunicate with utricle is a section called the ampula (boney)
contains crista ampullaris hair cells inside the cupula of the ampula

Question 8

BPPV

Answer 8

Free moving otoconia (calcium carbonate) particles in canal. As the head moves otoconia move through semicircular canals
90% related to posterior semicircular canals

Vertigo(spinning)
Loss of balance
Nausea/vomiting
DIX hallpike will have latent upbeat tortional nystagmus to affected side <1 min

Question 9

Vestibular neuritis

Answer 9

(Nerve condition) Unilateral vestibular hypofunction. Same as labyrinithitis without associated hearing loss

Dizziness/vertigo
Negative dix hallpike test (Not semicircular canals)
+ve VOR(head thrust) as vestibulooccular reflex will be affected
No hearing loss

Question 10

Meniers disease

Answer 10

Disorder of inner ear function that can cause hearing & vestibular dysfunction due to:

^ production of endolymph
decreased absorbtion of endolymph
decreased production of perilymph with increase in vol of endolyph sac

Causes: trauma, infection,vascular

Hearing loss
Vertigo
Tinnitus
Initially unilateral, progresses to bilateral, leads to deafness & vertigo dissapearing

Question 11

A patient has the following assessment findings explain the pathophysiology of each

1) visual tracking(saccades & smooth pursuit)=normal
2) Dix hallpike = Normal
3) VOR assessment (headthrust) = +ve on right

Answer 11

Unsteadyness indicates potential dizziness in particular with head movements indicates potential vestibular system pathology…

1) Visual tracking is controlled by the CNS
(Medial longitudinal fasiculus in SC) controlls eye movements such as saccades and smooth persuit
it is normal t/f no CNS damage
*issue must be peripheral

2) Dix hallpike normal t/f semicircular canals are not affected
>could be labyrinth(utricleor saccule)
>could be cranial nerve

3) VOR = +ve on right side
unilateral vestibular hypofunction t/f could be

> Vestibular neuritis (peripheral nerve)
Labyrinthitis(utricles or saccule) but will have hearing loss too

Question 12

Criteria for dix hallpike testing

Answer 12

Clear for vertebrobasillar insufficiency
Assess unaffected side first
Rotate head 45 degrees towards side you are testing
Tip head back 20-30 degrees below horozontal 
sitting to supine
stay there for 30 secs
keep eyes open
sit back up and monitor